Can You Be Too Clean?

Can You Be Too Clean? Early Exposure to Germs can Prevent Allergies and Asthma in Children.

Chances are you have at least one or all of these products in your home. What better way to make sure you and your family stay healthy, avoid germs, and prevent illness?

But what if germs could actually prevent your children from getting sick or acquiring chronic problems including allergies and asthma?

Old Theory: Hygiene Hypothesis

While it might seem counter-intuitive, a number of studies have shown that early exposure to germs may lead to reduced allergies and asthma in children. A number of studies suggested this connection, including ones that found a lower rate of allergies among children growing up on farms, and lower rates of hay fever among children with larger families. Both these studies suggest that something about a less hygienic environment lead to a lower rate of allergies.

For many years, this hygiene hypothesis proposed that we were making our environments too clean. And it seems that as cleanliness and hyper-sanitation rose, so did the rate of allergies in the population. By some estimates, the prevalence of allergies, asthma, and respiratory infections in the population has more than tripled.

Germs and the Immune System

To understand how germs may prevent allergies and asthma, we need to understand what germs are and how immune systems are built. Germs are microscopic entities that cause disease and include bacteria and viruses. They enter the body through the nose, the mouth, or cuts, and find the optimal environment to start reproducing. Our immune systems keep germs in check and prevent them from taking over our bodies.

The immune system works by sending out scouts that recognize the germs, mark them, and then destroy them. In the process, your body may break out in a fever, create mucus, and cause you cough and sneeze in order to stop the infection, kill the germs, and clear your body. (Allergies occur when the immune system overreacts to non-harmful triggers such as pollen.)

After fighting off an infection, the immune system remembers the particular strain of bacteria or virus, which can help it respond even faster if the body is infected again. But infants cannot rely on their immune systems like we can.

When children are born, their immune systems are not fully formed. For the first few months of life, an infant will rely on his mothers to pass along antibodies through breast milk and give his immune system a helping hand. As he grows, exposure to germs helps his immune systems learn, adapt, and become stronger. Each infection means giving the system a new tool against future infections. So being too clean is not a good thing.

New Theory: Old Friends Hypothesis

The old hygiene hypothesis suggested that we were making our environments too clean, and that our immune systems need to be stressed by disease. But it seems that this picture was too simple. A new study published just this month supports a different idea: the Old Friends hypothesis.

This hypothesis suggests that as humans evolved, the immune system grew dependent on exposure to common microbes (“old friends”) in order to grow. In contrast to dangerous microbes such as flu, polio, or smallpox, these helpful microbes taught the immune system how to function in order to eliminate harmful infections. But an immune system that doesn’t learn how to identify and fight infections is left unable to properly deal with allergens as well.

The study shows that it may not be clean environments that we have worry about, but our entire environment indoors and outdoors, which has slowly changed over the last few decades to be less conducive to beneficial microbes. Lifestyle changes—such as spending more time indoors—also limit our exposure to helpful bacteria outside while increasing our exposure to allergens inside, which accumulate in buildings due to well-sealed doors and windows.

How Germs Can be Good for You

So what can you do to ensure your children grow up happy and healthy?

For one, let children play outside in green spaces that have limited exposure to pollutants. Don’t be afraid of dirt and germs, but continue to maintain sanitary habits that can reduce the spread of harmful diseases like influenza. Also, make sure to vaccinate your children against deadly diseases such as measles and polio.

And remember that when the immune system successfully fights off disease, especially in young children, it grows stronger! Don’t focus on being too clean.